Aragonite mud, ooids and reefs: Neogene to Quaternary carbonate sedimentation on the North-West Shelf of Australia

澳大利亚西北大陆架（NWS）的远端陡峭的碳酸盐斜坡的大小相当于巴哈马群岛或波斯湾的碳酸盐系统，并形成了一个重要的模板古斜坡系统的解释。西北部在南纬13°至21°之间延伸，位于热带和亚热带之间的过渡地带。该大陆架上的碳酸盐沉积强烈地受区域海洋学的控制，该区域海洋学主要由南流、温暖、低盐度的Leeuwin海流和印度尼西亚洋流控制。海底的沉积物分布有很好的文献记载，但直到最近，有关北西海岸新近纪至更新世沉积剖面的信息还仅限于工业威尔斯钻井的岩屑和地球物理数据。2015年，IODP Expedition 356对北半球南部和中部的大陆边缘序列进行了岩心采集，以调查其自中新世中期以来的沉积历史。在这次考察期间收集的数据将首次将核心数据与广泛的2D和3D地震反射调查相结合，从而可以对从数十米到盆地规模的碳酸盐系统进行区域和详细的地貌研究。在该项目中，我们将：1）测试是否在西北部形成富含文石的低位楔，这将与经典的“高位脱落”概念相反; 2）分析导致几个富含非骨架颗粒的层段形成的环境条件，包括来自印度-太平洋地区的最古老的第四纪鲕粒; 3）建立与岩心资料相联系的地震和层序地层学解释，以调查北西中新世生物礁系统发育和淹没的环境控制因素。

The distally steepend carbonate ramp of the North West Shelf of Australia (NWS) equals in size the carbonate systems of the Bahamas or the Persian Gulf and forms an important template for the interpretation of ancient ramp systems. The NWS stretches between ~13° and 21°S and is situated at the transition between the tropical and sub-tropical realm. Carbonate sedimentation on this shelf is strongly controlled by regional oceanography, which is dominated by the south-flowing, warm, low-salinity Leeuwin Current and the Indonesian Throughflow. The sediment distribution on the sea-floor is well documented, but information on the Neogene to Pleistocene sedimentary section of the NWS was until recently limited to cuttings from industry wells and geophysical data. In 2015, IODP Expedition 356 cored the continental margin sequence of the southern and central part of the NWS to investigate its depositional history since the middle Miocene. Data collected during this expedition will allow for the first time to integrate core data with extensive 2D and 3D seismic-reflection surveys allowing regional and detailed geomorphological studies of the carbonate system from the tens-of-meters to basin scale. Within the project we will: 1) test if an aragonite rich lowstand wedge forms at the NWS, which would be reverse to the classical "highstand shedding" concept; 2) analyse the environmental conditions that led to the formation of several intervals rich in non-skeletal grains including the oldest Quaternary ooids from the Indo-Pacific region; 3) establish a seismic and sequence stratigraphic interpretation tied to core data to investigate the environmental controls for the development and drowning of the Miocene reef system on the NWS.